Source liquid supply apparatus having a cleaning function

ABSTRACT

A source liquid supply apparatus and method that avoids leaving source liquid-and/or cleaning fluid-derived residues in the vicinity of the connection region between the source liquid feed conduit and the source tank. A flow-switching mechanism is attached to the source tank of a source liquid supply apparatus. This flow-switching mechanism has a first port connected to the discharge port conduit of the source tank, a second port connected to a feed conduit, and a third port connected to an exhaust conduit. The first port can be closed by a valve member on a diaphragm disposed within a common compartment while communication is maintained between the second and third ports. A cleaning fluid source and a purge gas source are connected to the feed conduit. Purge gas and cleaning fluid fed into the feed conduit are discharged from the second and third ports and through the exhaust conduit.

This application is a 371 of International PCT ApplicationPCT/EP2002/013491, filed Nov. 13, 2002.

BACKGROUND OF THE INVENTION

This invention relates to a source liquid supply apparatus having acleaning function, to a method for detaching the source tank from saidsupply apparatus, and to a method for cleaning a source liquid feedconduit. More particularly, this invention relates to the structure ofan apparatus for supplying a source liquid, such as a chemical reagent,to a particular facility, for example, to a metalorganic chemical vapordeposition (MOCVD) apparatus. The invention additionally relates to amaintenance technology for said supply apparatus.

The equipment used to fabricate semiconductor devices and electronicdevices and instruments frequently employs source liquids in the form ofdifficult-to-handle chemical reagents whose residues are difficult toremove simply by a gas purge. Once such a source liquid has passedthrough, for example, a manifold or vaporizer, the interior thereofcannot be satisfactorily treated by purging and cleaning with just asimple gas purge cycle (repetitive pressurization with gas and vacuumexhaust) when it is desired to carry out maintenance or exchange oralter the reagent. A known technology that addresses this problemcomprises the use, in addition to the gas purge, of a solvent as acleaning fluid in order to achieve good purging and cleaning of thetarget compartment.

An apparatus that employs this particular technology is disclosed inU.S. Pat. No. 5,964,230. This apparatus, which carries out solvent-basedpurging and cleaning of a chemical-handling manifold, introduces solventinto the manifold through a nozzle disposed coaxially with respect tothe manifold and employs a mechanical scrubbing operation in addition toresidue dissolution.

U.S. Pat. No. 6,033,479 discloses a process gas delivery apparatus forMOCVD applications that employs an auxiliary cleaning apparatus. Aslanted cleaning fluid feed pipe is provided in this system in order tofeed cleaning fluid into the process gas delivery apparatus and fordischarge of the waste cleaning fluid. This system also contains anoptical sensor in the process gas feed pipe in order to determine themaintenance time automatically. This optical sensor can be used both todetect the accumulation of deposited material in the piping and todetect cleaning fluid remaining within the piping after the cleaningprocess.

U.S. Pat. No. 5,362,328 discloses an apparatus and method for feedingsource reagent in vaporized form into a CVD process compartment. In thiscase, an auxiliary cleaning apparatus is used in order to protect thesource reagent vaporizer from the negative influence of solid depositsproduced during the CVD process. For example, when it is desired to feedrelatively nonvolatile source reagent to the CVD process compartment,the vaporizer may be configured with a large surface area having a highheat transfer efficiency. When such a vaporizer is used in a CVD system,by-products are produced in the vaporizer section from the sourcereagent, which causes clogging and lowers the vaporizing efficiency. Thetechnology disclosed in U.S. Pat. No. 5,362,328 solves these problems byimplementing a periodic cleaning of the vaporizer with an auxiliarycleaning apparatus.

U.S. Pat. No. 4,738,693 (Japanese Laid Open (Kokai or Unexamined) PatentApplication Number Sho 64-27616 (27,616/1989)) teaches an apparatus fordistributing and purifying semiconductor source reagents. This apparatusis provided with a receptacle and valve block that can be joined to eachother in a leaktight manner. The valve block is provided with first andsecond ports for feeding source reagent and with a purge port foreffecting purging. Prior to feeding source reagent, the purge port isopened—while the first and second ports are closed—in order to eliminategas remaining in the dead spaces from the first and second ports and thegas flow passages.

An apparatus for reagent supply is disclosed in U.S. Pat. No. 6,199,599(issued 13 Mar. 2001); this apparatus employs at least three purgesources for the purpose of purging reagent from the piping system. Forexample, a vacuum source, solvent source, and inert gas source are usedas three purge sources, wherein the solvent is expelled from the systemaccompanying feed of the inert gas.

A problem common to the type of prior art systems under consideration,including the systems taught in the United States patents listed above,is the presence of a difficult-to-purge dead space in the vicinity ofthe joint or connection between the source tank and the conduit forfeeding source liquid to the process apparatus. As a consequence, evenafter the piping has been purged, substances such as source liquid,cleaning fluid, and semidecomposed materials therefrom can easily remainwithin this dead space. When, for example, these residues come intocontact with air when the source tank is exchanged, they formdifficult-to-remove substances that clog the piping or producesubstances that poison the process. Taking as an example the use of PET(pentaethoxytantalum) to form high dielectric films, upon contact withair this reagent reacts with O₂ and H₂O to form a gel-like material. Inthe case of TiCl₄ the reaction of this compound with H₂O results in theproduction of HCl, a chemical that lowers the film-forming rate.

This invention was developed in view of the problems delineated abovefor the prior art. An object of this invention is to provide a sourceliquid supply apparatus that incorporates a cleaning function and thatavoids leaving source liquid- and/or cleaning fluid-derived residues inthe vicinity of the joint or connection region between the source liquidfeed conduit and the source tank. An additional object of this inventionis to provide a method for detaching the source tank from the foregoingapparatus. A further object of this invention is to provide a method forcleaning a source liquid feed conduit.

SUMMARY

This invention relates to a source liquid supply apparatus and method ofoperation which includes using a pressurized gas, in addition to a purgegas, with a leaktight source tank having a discharge port and apressurization port. A pressurization gas conduit along with aflow-switching mechanism which is attached to the discharge portoperates in such a manner that prevents residue buildup from the sourceliquid or the cleaning fluid in the system and consequently reduces thepossibility of impurity contamination in an ultra-high purity feedsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects for the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like elements are given the same or analogous reference numbersand wherein:

FIG. 1 illustrates the conduit layout in an MOCVD system that producestantalum oxide film and that incorporates a source liquid supplyapparatus.

FIG. 2( a) illustrates a vertical cross-section of the internalstructure of the flow-switching mechanism.

FIG. 2( b) illustrates a horizontal cross-section of the internalstructure of the flow-switching mechanism.

FIG. 3 illustrates the sequence for exchanging the source tank usingexemplary embodiments of the inventive method for cleaning a sourceliquid feed conduit and the inventive method for detaching the sourcetank.

FIG. 4 illustrates an embodiment of a source liquid supply apparatus.

FIG. 5 illustrates a second embodiment of a source liquid supplyapparatus.

FIG. 6 illustrates a vertical cross section of a modified example of aflow-switching mechanism.

FIG. 7( a) illustrates a vertical cross-section of a flow-switchingmechanism.

FIG. 7( b) illustrates a horizontal cross-section of a flow-switchingmechanism.

FIG. 8 illustrates a third embodiment of a source liquid supplyapparatus.

FIG. 9 illustrates the structure of a sampling section that wasincorporated in place of the waste tank structure in experiments carriedout using the apparatus illustrated in FIG. 8.

FIG. 10 illustrates the sequence of an exemplary embodiment of theinventive method for cleaning a source liquid feed conduit.

FIG. 11 compares the cleaning efficacy of a comparative example EC(continuous treatment) and an example EB (batch treatment) that is anexemplary embodiment of this invention.

FIG. 12 illustrates a fourth embodiment of a source liquid supplyapparatus.

FIG. 13 illustrates a fifth embodiment of a source liquid supplyapparatus.

FIG. 14 illustrates a sixth embodiment of a source liquid supplyapparatus.

FIG. 15 illustrates a seventh embodiment of a source liquid supplyapparatus.

FIG. 16 illustrates an eighth embodiment of a source liquid supplyapparatus.

DESCRIPTION OF PREFERRED EMBODIMENTS

The first aspect of the invention is a source liquid supply apparatusthat is characteristically provided with

-   a leaktight source tank that contains source liquid and that is    provided with a discharge port for the output of said source liquid    and a pressurization port for the introduction of pressurization gas    for the pressure-delivery of said source liquid;-   a pressurization gas conduit for the feed of the aforesaid    pressurization gas into the source tank, wherein said pressurization    gas conduit connects the aforesaid pressurization port and a source    of pressurization gas;-   a flow-switching mechanism that is attached to the aforesaid    discharge port and which is provided with    -   a first port, wherein said first port is connected to said        discharge port,    -   a second and third ports, which are connected to each other        through an intermediate flow passage and which are connected to        the first port, and    -   a valve member that can produce an isolated state in which        communication between the first port and the second and third        ports is closed off while communication between the second and        third ports is maintained;-   a feed conduit that connects the second port to a prescribed    facility in order to supply the aforesaid source liquid to said    facility;-   a cleaning fluid conduit that connects the aforesaid feed conduit    with a source of cleaning fluid in order to feed cleaning fluid into    the feed conduit;-   a purge gas conduit that connects the feed conduit to a source of    purge gas in order to feed purge gas into the feed conduit; and-   an exhaust conduit that connects to the third port and that, when    the aforesaid isolated state is in place, exhausts the cleaning    fluid and purge gas that have been introduced into the feed conduit,    wherein said exhaust proceeds through the aforesaid second port,    intermediate flow passage, and third port.

The second aspect of this invention comprises the apparatus of the firstaspect with the characteristic features that the first, second, andthird ports are each connected, through first, second, and thirdorifices, respectively, to a common compartment that functions as partof the intermediate flow passage, and the aforesaid valve member has theability to close the first orifice while the second and third orificesremain open.

The third aspect of this invention comprises the apparatus of the firstaspect with the characteristic features that the first port is connectedthrough a first orifice to a common compartment that functions as partof the intermediate flow passage, the second and third ports areconnected to each other through a connection that does not proceedthrough said common compartment and are connected to said commoncompartment through a common orifice, and the aforesaid valve member hasthe ability to close said common orifice.

The fourth aspect of this invention comprises an apparatus as describedin any of the first through third aspects, with the characteristicfeature that the aforesaid valve member is supported by a bellows ordiaphragm that forms a part of the inner wall of the common compartment.

The fifth aspect of this invention comprises an apparatus as describedin any of the first through fourth aspects, with the characteristicfeature that a vacuum exhaust member is connected to the exhaustconduit.

The sixth aspect of this invention comprises an apparatus as describedin any of the first through fifth aspects, with the characteristicfeatures that a first mounting valve is disposed in the feed conduit inthe vicinity of the second port, a second mounting valve is disposed inthe exhaust conduit in the vicinity of the third port, and theflow-switching mechanism is detachable from said first and secondmounting valves.

The seventh aspect of this invention comprises a method for detachingthe source tank from the source liquid supply apparatus of the sixthaspect, said method being characteristically provided with a residualliquid discharge process, in which the exhaust conduit or source tank isdepressurized and, utilizing the pressure difference produced by saiddepressurization, source liquid remaining within the feed conduit isdischarged into the exhaust conduit or source tank; a cleaning process,which is carried out after the aforesaid residual liquid dischargeprocess and in which, with the aforesaid isolated state being in placeand the exhaust conduit closed, cleaning fluid is fed from the cleaningfluid conduit into the feed conduit so as to fill the interiors of thefeed conduit, second port, intermediate flow passage, and third portwith cleaning fluid, and in which the exhaust conduit is thereafteropened and the cleaning fluid is discharged into the exhaust conduit; agas purge process, which is carried out after the aforesaid cleaningprocess and in which, with the aforesaid isolated state being in placeand the exhaust conduit closed, purge gas is fed from the purge gasconduit into the feed conduit so as to fill the interiors of the feedconduit, second port, intermediate flow passage, and third port withpurge gas, and in which the exhaust conduit is thereafter opened and thepurge gas is discharged into the exhaust conduit; and a detachmentprocess, which is carried out after the aforesaid purge process and inwhich the flow-switching mechanism and the source tank are togetherdetached from the source liquid supply apparatus by detaching theflow-switching mechanism from the first and second mounting valves.

The eighth aspect of this invention comprises the method of the seventhaspect, which is characteristically additionally provided with a processwhich is carried out after the aforesaid detachment process and in whichthe feed conduit and exhaust conduit are interconnected through thefirst and second mounting valves and purge gas is flowed from the purgegas conduit through the feed conduit and into the exhaust conduit.

The ninth aspect of this invention comprises the method of the seventhor eighth aspect characterized by the repetition in the cleaning processof the feed operation in which cleaning fluid is fed into the feedconduit and a discharge operation in which cleaning fluid is dischargedinto the exhaust conduit by the feed of purge gas into the feed conduit.

The tenth aspect of this invention comprises the method of the ninthaspect characterized in that in the discharge operation the interior ofthe feed conduit is first pressurized to 0.1 to 1 MPa by the feed ofpurge gas with the exhaust conduit closed and the exhaust conduit isthereafter opened.

The eleventh aspect of this invention is a method for cleaning a targetsection of a feed conduit that connects a source tank with a prescribedfacility for the purpose of feeding source liquid to said facility, saidmethod being characteristically provided with a preparatory process, inwhich a state is set up in which

-   -   a first valve is disposed at one of the two ends of said target        section and a second valve is disposed at the other end, in        order to thereby enable selective closure of the two ends of        said target section,    -   a cleaning fluid source and a purge gas source are connected to        one side of said target section through, respectively, a        cleaning fluid valve and a purge gas valve, for the purpose of        feeding, respectively, cleaning fluid and purge gas thereinto,        and    -   a waste tank for the purpose of recovering waste liquid is        connected through a waste valve to the other side of said target        section;

-   a residual liquid discharge process, which is carried out after the    preparatory process and in which source liquid remaining in the    target section is discharged to the source tank or waste tank;

-   a cleaning process, which is carried out after the residual liquid    discharge process and which comprises repetition of a feed operation    in which cleaning fluid is fed into the target section with the    waste valve closed and a discharge operation in which with the waste    valve open the cleaning fluid is discharged into the waste tank    while feeding purge gas; and

-   a gas purge process, which is carried out after the cleaning process    and in which the interior of the target section is subjected to a    gas purge by the purge gas.

The twelfth aspect of this invention comprises the method according tothe eleventh aspect characterized in that one of the aforesaid first andsecond valves is provided with a flow-switching mechanism that has

-   -   a first port that is connected to the source tank,    -   a second and third ports, which are connected to each other        through an intermediate flow passage and which are connected to        the first port, and    -   a valve member that can produce an isolated state in which        communication between the first port and the second and third        ports is closed off while communication between the second and        third ports is maintained,        and in that said second port is connected through the target        section to the aforesaid facility and the said third port is        connected to the cleaning fluid source and the purge gas source        or the waste tank.

The thirteenth aspect of this invention comprises the method accordingto the twelfth aspect characterized in that the first, second, and thirdports are each connected, through first, second, and third orifices,respectively, to a common compartment that functions as part of theintermediate flow passage, and in that the aforesaid valve member hasthe ability to close the first orifice while the second and thirdorifices remain open.

The fourteenth aspect of this invention comprises a method according toany of the eleventh through thirteenth aspects characterized in that inthe discharge operation the interior of the target section is firstpressurized to 0.1 to 1 MPa by the feed of purge gas with the exhaustvalve closed and the exhaust valve is thereafter opened.

The fifteenth aspect of this invention comprises a method according toany of the eleventh to fourteenth aspects, characterized in that theaforesaid cleaning process is provided with

-   a cleaning fluid feed process, in which, with the purge gas valve,    first and second valves, and waste valve closed, the cleaning fluid    valve is opened and cleaning fluid is fed from the cleaning fluid    source to the target section;-   a pressurization process, which follows the cleaning fluid feed    process and in which, with the cleaning fluid valve, first and    second valves, and waste valve closed, the purge gas valve is opened    and the interior of the target section is pressurized to 0.1 to 1    MPa by the feed of purge gas from the purge gas source to the target    section; and-   a discharge process, which follows the pressurization process and in    which, with the cleaning fluid valve and first and second valves    closed and with the purge gas valve open, the waste valve is opened    and the cleaning fluid is discharged into the waste tank while purge    gas is supplied.

The sixteenth aspect of this invention comprises a method according toany of the eleventh to fifteenth aspects, said method beingcharacterized in that in the cleaning process the interior of the targetsection is brought into a reduced pressure state prior to feed of thecleaning fluid into the target section.

The seventeenth aspect of this invention comprises a method according toany of the eleventh to sixteenth aspects, said method beingcharacterized in that cleaning fluid pressurized to 0.1 to 1 MPa is fedinto the target section in the cleaning process.

The embodiments of this invention explore a variety of executions ofthis invention, and various embodiments of this invention can be derivedby suitable combination of the plural number of disclosed constituentelements. For example, when an embodiment of the invention has beenderived in which some constituent elements have been omitted from theoverall set of constituent elements presented for the embodiment, theseomitted elements can be suitably fulfilled by conventional well-knowntechnologies in the actual working of the derived inventive embodiment.

EMBODIMENTS OF THE INVENTION

Embodiments of this invention are explained below with reference to thedrawings. In the description that follows, constituent elements thathave approximately the same structure and function are assigned the samereference symbol and their description will be repeated only whennecessary.

FIG. 1 contains a schematic drawing of the conduit layout in an MOCVDsystem that produces tantalum oxide (Ta₂O₅) film. This MOCVD systemincorporates a source liquid supply apparatus that is an embodiment ofthis invention. More specifically, this system is provided with an MOCVDapparatus 10 and a source liquid supply apparatus 20.

The MOCVD apparatus 10 contains a leaktight process compartment 12, inthe interior of which is disposed a susceptor 13 that can hold, support,and heat a semiconductor wafer W. The process compartment 12 isconnected to a vacuum exhaust member 14 that can exhaust the interior ofthe process compartment 12 and can establish a vacuum therein. Theprocess compartment 12 is also connected to a feed conduit 16 that cansupply PET (pentaethoxytantalum: Ta(OC₂H₅)₅=the tantalum source liquid)and to a feed conduit 18 that can supply, for example, O₂ (oxidizer).Said feed conduit 16 is connected to a source liquid supply apparatus 20that is an embodiment of this invention, while said feed conduit 18 isconnected to an O₂ source 19. A vaporizer 17 is disposed directlyupstream from the process compartment 12 in the feed conduit 16; thisvaporizer 17 functions to vaporize the PET.

The source liquid supply apparatus 20 contains a leaktight source tank22 that holds the PET source liquid. There are disposed on the sourcetank 22 a discharge port conduit 24 for delivery of the source liquidand a pressurization port conduit 26 for introducing pressurization gasfor the pressure-delivery of the source liquid. This pressurization portconduit 26 is connected to a pressurization gas source 28 that cansupply an inert gas, e.g., helium, through a pressurization gas conduit27 itself provided with a valve Vp. A flow-switching mechanism Vc (firstvalve) is connected to the discharge port conduit 24.

FIGS. 2( a) and 2(b) contain, respectively, vertical and horizontalcross-sectional drawings that schematically illustrate the internalstructure of the flow-switching mechanism Vc. As shown, theflow-switching mechanism Vc contains a first port 33, a second port 34,and a third port 35 formed within a leaktight casing 32 and contains anintermediate flow passage 36 that interconnects said ports. A commoncompartment 38 is elaborated as part of the intermediate flow passage36, and the first, second, and third ports 33, 34, and 35 are connected,through first, second, and third orifices 33 a, 34 a, and 35 a,respectively, to the common compartment 38.

The ceiling of the common compartment 38 is defined by the diaphragm 42,while the center of the diaphragm 42 is structured as a valve member 43that can open and close the first orifice 33 a of the first port 33. Thediaphragm 42 is driven up-and-down by a spindle (not shown) disposed onthe top thereof, and the valve member 43 is opened and closedaccompanying the up-and-down movement of the diaphragm 42. The valvemember 43 can effect opening (position indicated by the dashed line inFIG. 2( a)) and closure (position indicated by the solid line in FIG. 2(a)) of the first orifice 33 a while the second orifice 34 a and thethird orifice 35 a remain open. In other words, when the valve member 43is in the position indicated by the solid line in FIG. 2( a), the secondport 34 and the third port 35 are in communication with each otherthrough the common compartment 38 while communication between the firstport 33 and the second port 34 and third port 35 is cut off (closedstate=isolated state).

Usable as the flow-switching mechanism Vc are the DF series, multivalvemanifold, 6LV-F5V (product of the NUPRO Co.) and the Mega 1 series,direct diaphragm valve, FUDDFTRO-71G (product of Kabushiki KaishaFujikin).

The discharge port conduit 24 of the source tank 22 is connected to thefirst port 33, while the second port 34 is connected to the upstreamsection 16 a of the feed conduit 16 that supplies the PET source liquid.The third port 35 is connected to an exhaust conduit 25 for thedischarge of the fluid within the feed conduit 16. A valve V4 isdisposed in the upstream section 16 a of the feed conduit in thevicinity of the second port 34, while a valve V5 is disposed in theexhaust conduit 25 in the vicinity of the third port 35. Flanges Fc1 andFc2 are respectively provided on the second and third ports 34 and 35and flanges F4 and F5 are respectively provided on valves V4 and V5 soas to render the flow-switching mechanism Vc attachable to anddetachable from the valves V4 and V5.

The upstream section 16 a of the feed conduit is connected to thedownstream section 16 b of the feed conduit through a manifold 52. Thismanifold 52 is connected through a cleaning fluid conduit 54 to acleaning fluid source 55 that can supply cleaning fluid for dissolutionof residues originating with the PET; this cleaning fluid is a suitablesolvent such as an alcohol, ketone, or ether. The manifold 52 is alsoconnected through a purge gas conduit 56 to a purge gas source 57 thatcan supply an inert gas such as nitrogen. The manifold 52 is connectedto the conduits 54, 56, and 16 b through valves V1, V2, and V3(V3=second valve), respectively.

The exhaust conduit 25 is connected to a waste tank 62 for the recoveryof waste solutions and to a vacuum exhaust member 63 that is capable ofdepressurizing and exhausting the interior of the exhaust conduit 25.Two port conduits 64 and 66 are disposed on the waste tank 62; these twoport conduits 64 and 66 are connected to one another through the bypassconduit 65. The exhaust conduit 25 is connected to one end of the bypassconduit 65, while the vacuum exhaust member 63 is connected to the otherend of the bypass conduit 65. Valves V7, V8, and V9 are disposed,respectively, in the conduits 64, 65, and 66.

An embodiment of the inventive method for cleaning the source liquidfeed conduit and an embodiment of the inventive method for detaching thesource tank will now be explained with reference to the source liquidsupply apparatus 20 in FIG. 1. FIG. 3 contains a flow chart that laysout the sequence for changing out the source tank using the inventivemethods.

During a typical treatment the valves Vp, Vc, V4, and V3 will be openwhile all the other valves will be closed. Under these circumstances,pressurization gas is introduced into the source tank 22 through thepressurization port conduit 26, which results in source liquid transportout of the discharge port conduit 24 and supply of PET (source liquid)through the feed conduit 16 into the MOCVD apparatus 10.

The sequence outlined below is followed when it is desired to detach thesource tank 22, for example, in order to exchange the source tank 22. Itis assumed in the explanation that follows that all the valves areinitially set to the state corresponding to typical treatment asspecified above (valves Vp, Vc, V4, and V3=open, all othervalves=closed).

The source liquid remaining in the feed conduit 16 is first discharged(process S1).

This process is initiated with the following operations: the valves V9and V7 are opened and the valves V3 and Vc are closed (the valve V5 isalso in a closed state at this point) and the waste tank 62 and exhaustconduit 25 are depressurized by the vacuum exhaust member 63. The valveV5 is then opened and, due to the pressure difference generated by thedepressurization operation between the upstream section 16 a of the feedconduit and the waste tank 62 and exhaust conduit 25, source liquidremaining in said upstream section 16 a of the feed conduit is recoveredinto the waste tank 62 through the exhaust conduit 25. As necessary thisprocess is repeated until the source liquid in the upstream section 16 aof the feed conduit has been completely recovered.

The depressurization operation performed on the waste tank 62 andexhaust conduit 25—an operation which is necessary for the discharge ofresidual source liquid—can be carried out as a preliminary step duringtypical treatment, or the waste tank 62 and exhaust conduit 25 can becontinuously maintained under reduced pressure (except during detachmentof the source tank 22). In addition, opening and closing of the valvesV2 and V5 can be repeated during source liquid recovery in order to alsoutilize purge gas fed from the purge gas source 57 for source liquidrecovery.

The source liquid may also be recovered into the source tank 22 ratherthan the waste tank 62. In this case, the source tank 22 is firstdepressurized by a suitable means and the valve Vc is then opened andsource liquid is recovered into the source tank 22 utilizing thepressure difference between the source tank 22 and the upstream section16 a of the feed conduit. Although not shown, configurations that wouldenable depressurization of the source tank 22 are, for example,connection of a valve-equipped vent conduit or a vacuum exhaust memberto the pressurization gas conduit 27.

The interior of the flow-switching mechanism Vc is then cleaned withcleaning fluid (process S2).

This process is begun as follows: the valve V1 is opened and the valveV5 is closed (the valves V2, V3, and Vc are also in a closed state atthis point) and the upstream section 16 a of the feed conduit and thesecond and third ports 34 and 35 and common compartment 38 of theflow-switching mechanism Vc are filled with cleaning fluid supplied fromthe cleaning fluid source 55. This condition is maintained for a periodof time suitable for dissolution of PET-originating residues, forexample, 30 seconds. The valve V1 is then closed and the valves V2 andV5 are opened and, utilizing purge gas supplied from the purge gassource 57, the loaded cleaning fluid is recovered into the waste tank 62through the exhaust conduit 25. This procedure is repeated until theresidues within the second and third ports 34 and 35 and commoncompartment 38 of the flow-switching mechanism Vc are entirely cleanedout.

The interior of the flow-switching mechanism Vc is then purged with gas(process S3).

This process is begun as follows: the valve V2 is opened and the valveV5 is closed (the valves V1, V3, and Vc are also in a closed state atthis point) and the upstream section 16 a of the feed conduit and thesecond and third ports 34 and 35 and common compartment 38 of theflow-switching mechanism Vc are filled with purge gas supplied from thepurge gas source 57. The valve V2 is then closed and subsequent theretothe valve V5 is opened and the purge gas is discharged through theexhaust conduit 25. This procedure is repeated until there are no tracesof cleaning fluid remaining within the second and third ports 34 and 35and common compartment 38 of the flow-switching mechanism Vc.

The source tank 22 is then detached (process S4).

This process commences with the opening of the valve V2 and, while purgegas is flowing from the purge gas source 57 in the upstream section 16 aof the feed conduit, closing the valves V4 and V5. The connectionsbetween the flanges F4 and F5 on the valves V4 and V5 and the flangesFc1 and Fc2 on the flow-switching mechanism Vc are then released and thesource tank 22 and the flow-switching mechanism Vc are together detachedfrom the valves V4 and V5, that is, from the source liquid supplyapparatus 20.

When the source tank 22 is to remain detached for some period of time(NO in process S5), it will be desirable for the valves V4 and V5 to beconnected to each other, either directly or through a connection unit.In addition, an idle purge (process S6) should be maintained within theupstream section 16 a of the feed conduit by opening valves V2, V4, V5,and V8, closing valves V7 and V9, and feeding purge gas from the purgegas source 57. This can prevent the introduction of air into theupstream section 16 a of the feed conduit during detachment of thesource tank 22. When, on the other hand, a fresh source tank 22 providedwith its own flow-switching mechanism Vc has already been set up at thetime point at which the spent source tank 22 is detached, an immediateexchange of the source tanks can be carried out (YES in process S5).

With the valves V4 and V5 closed, a fresh source tank 22 is installedbetween said valves V4 and V5 (process S7). The valve V5 is then openedwith the flow-switching mechanism Vc remaining closed, and the air thathas infiltrated between the valves V4 and V5 during installation isexhausted through the exhaust conduit 25 (process S8). The shift is thenmade to the typical treatment in which PET is fed from the fresh sourcetank 22 to the MOCVD apparatus 10 based on the demand by the MOCVDapparatus 10. This shift to the typical treatment can be preceded, asnecessary or desired, by cleaning/discharge/purge/vacuum exhaust of theinterior of the upstream section 16 a of the feed conduit.

The conduit diagram in FIG. 1 simply depicts an example, in which inparticular the valves are represented in terms of their functionality.The valves are therefore not limited to particular types. For example,the functions of the valves V4 and V5 can be built into theflow-switching mechanism Vc, while other conduit sections can bemodified as shown in FIGS. 4 and 5.

FIG. 4 contains a conduit diagram that schematically illustrates asource liquid supply apparatus that is another embodiment of thisinvention. The apparatus in this embodiment differs from the apparatusin FIG. 1 by not using the manifold 52 to connect the cleaning fluidsource 55 and the purge gas source 57 to the feed conduit 16.Specifically, the cleaning fluid conduit 54 and the purge gas conduit 56are connected in this case to the feed conduit 16 through the usualtwo-way valves V1 and V2.

FIG. 5 contains a conduit diagram that schematically illustrates asource liquid supply apparatus that is yet another embodiment of thisinvention. The apparatus in this embodiment differs from the apparatusin FIG. 1 by using two three-way valves V11 and V13 (V13=second valve)instead of the manifold 52 in order to connect the cleaning fluid source55 and the purge gas source 57 to the feed conduit 16. Specifically, thecleaning fluid conduit 54 and the purge gas conduit 56 are connected toeach other through two ports of the three-way valve V11. The oneremaining port on the three-way valve V11 is connected across the valve12 to one port on the three-way valve V13. The two remaining ports onthe three-way valve V13 are used to connect the upstream section 16 a ofthe feed conduit with the downstream section 16 b of the feed conduit.The flow-switching mechanism Vc illustrated in FIGS. 2( a) and (b) canbe used as a three-way valve V11 or V13.

FIG. 6 contains a vertical cross section that illustrates a modifiedexample of the flow-switching mechanism Vc that is another embodiment ofthis invention. The mechanism in this embodiment differs from themechanism in FIG. 2 by the use of a bellows 45 in place of the diaphragm42. In this case, the end of a bellows 45 bears the valve member 43 foropening/closing the first orifice 33 a of the first port 33 thatconnects to the source tank 22. This valve member 43 effects opening andclosing of the first port 33 accompanying the expansion and contractionof the bellows 45.

FIGS. 7( a) and (b) contain, respectively, a vertical cross section anda horizontal cross section that illustrate another modified example ofthe flow-switching mechanism Vc that is yet another embodiment of thisinvention. In the mechanism of this embodiment, the first port 33(connected to the source tank 22) is connected through a first orifice33 a to a common compartment 48 that functions as part of theintermediate flow passage 46. The second and third ports 34 and 35,which are respectively connected to the feed conduit 16 and the exhaustconduit 25, are connected to each other through a connection that doesnot proceed through the common compartment 48 and are connected to thecommon compartment 48 by a common orifice 46 a. The valve member 43, byclosing off the common orifice 46 a, closes off the communicationbetween the first port 33 and the second and third ports 34 and 35(closed state=isolated state). A bellows can also be used in this casefor actuation of the valve member 43 instead of the diaphragm 42.

FIG. 8 contains a conduit diagram that schematically illustrates asource liquid supply apparatus that is yet another embodiment of thisinvention. The apparatus in this embodiment, while having almost thesame structure as the apparatus illustrated in FIG. 5, additionallyillustrates a cleaning fluid source 55 that employs gas pressuredelivery. A needle valve NV is also disposed between the valve V2 andthe purge gas source 57 for the purpose of controlling the gas flow ratein the purge gas conduit 56. A flow-switching mechanism as illustratedin FIGS. 2( a) and (b) is used as the three-way valve V11 and as thethree-way valve V13.

Specifically, the cleaning fluid source 55 contains a leaktight cleaningfluid tank 72 that holds ethanol for cleaning out PET (source liquid).There are disposed on this cleaning fluid tank 72 a discharge portconduit 74 for delivery of the source liquid and a pressurization portconduit 76 for introducing pressurization gas for the pressure-deliveryof the source liquid. This pressurization port conduit 76 is connectedto a pressurization gas source 78 that can supply an inert gas, e.g.,helium, through a pressurization gas conduit 77 itself provided with avalve VS1. The discharge port conduit 74 is connected to the cleaningfluid conduit 54 through a valve VS2.

Another embodiment of the inventive method for cleaning a source liquidfeed conduit will now be explained with reference to the source liquidsupply apparatus illustrated in FIG. 8. FIG. 10 contains a flow chartthat lays out the sequence of this method. The cleaning target sectionin this case comprises the upstream section 16 a of the feed conduit andvalves Vc, V4, V5, V12, and V13.

The set up or preparation required to carry out cleaning is firstperformed (process S11).

In the embodiment under consideration, valves Vc and V13 (the first andsecond valves) are provided as preparatory elements required forcleaning; these valves are disposed so as to enable selective closure ofthe two ends of the target section, i.e., the upstream section 16 a ofthe feed conduit. A cleaning fluid source 55 and a purge gas source 57are also connected, respectively through a cleaning fluid valve V11 anda purge gas valve V2, on one side of the target section (the upstreamsection 16 a of the feed conduit) for the purpose of supplying,respectively, cleaning fluid and purge gas. A waste tank 62 is connectedthrough a waste valve V5 on the other side of the target section (theupstream section 16 a of the feed conduit) for the purpose of recoveringwaste liquid. In the embodiment under consideration these preparatoryelements were incorporated into the source liquid supply apparatus whenthe apparatus was set up. The cleaning fluid source 55, purge gas source57, and waste tank 62, however, may be connected to the cleaning targetsection just during cleaning.

The sequence outlined below is followed when it is desired to clean thefeed conduit 16 on the occasion of, for example, exchanging the sourcetank 22. The initial settings here are as follows: after all the valveshave been closed, the valves VS1 and VS2 are opened and the needle valveNV is set so as to give a flow rate of 10-100 L/min at atmosphericpressure.

In the case of the valves V11, V13, and Vc, the closed condition denotesa condition, as illustrated by the solid line in FIG. 2( a), in whichthe first port 33 is closed off from the second and third ports 34 and35 while communication is maintained between the second and third ports34 and 35. Thus, the closed valve V11 resides in a state in which theline to the cleaning fluid source 55 is closed off from the upstreamsection 16 a of the feed conduit while the line to the purge gas source57 communicates with the upstream section 16 a of the feed conduit. Theclosed valve V13 resides in a state in which the line to the MOCVDapparatus 10 is closed off from the upstream section 16 a of the feedconduit while the line to the cleaning fluid source 55 and purge gassource 57 communicates with the upstream section 16 a of the feedconduit. The closed valve Vc resides in a state in which the line to thesource tank 22 is closed off from the upstream section 16 a of the feedconduit while the line to the waste tank 62 communicates with theupstream section 16 a of the feed conduit.

Residual source liquid in the cleaning target section is firstdischarged (process S12).

The valves V9, V7, V2, V12, V4, and V5 are opened in this process in thegiven sequence in order to feed purge gas from the purge gas source 57into the cleaning target section (upstream section 16 a of the feedconduit) and conduct a vacuum exhaust on the same section using thevacuum exhaust member 63. Utilizing the purge gas this functions torecover source liquid remaining in the upstream section 16 a of the feedconduit through the exhaust conduit 25 to the waste tank 62.

Recovery of the source liquid can also be effected by performing apreliminary depressurization of the waste tank 62 and exhaust conduit 25using the vacuum exhaust member 63 and then utilizing the pressuredifference between the upstream section 16 a of the feed conduit and thewaste tank 62 and exhaust conduit 25.

The source liquid can also be recovered to the source tank 22 ratherthan to the waste tank 62. In such a case, the source tank 22 is firstdepressurized by a suitable means and the source liquid is thenrecovered to the source tank 22 by opening Vc and utilizing the pressuredifference between the upstream section 16 a of the feed conduit and thewaste tank 22. Although not shown, configurations that would enabledepressurization of the source tank 22 are, for example, connection of avalve-equipped vent conduit or a vacuum exhaust member to thepressurization gas conduit 27.

The interior of the cleaning target section is then depressurized(process S13).

In this process, the vacuum exhaust member 63 remains in operation whileonly the valve V2 is closed relative to the situation in theabove-described process S12; this condition is maintained for 1 to 100seconds. As a consequence, the interior of the upstream section 16 a ofthe feed conduit is depressurized by the vacuum exhaust member 63 to 1to 30 kPa and preferably to around the vapor pressure of the cleaningfluid at ambient temperature (5.8 kPa at 20° C. for ethanol).

Cleaning fluid is then fed into the interior of the cleaning targetsection (process S14).

Relative to the situation in the above-described process S13, the valveV5 is closed and the valve V11 is opened in the instant process, and asa consequence cleaning fluid is fed from the cleaning fluid source 55into the upstream section 16 a of the feed conduit. At this point, thecleaning fluid can as necessary or desired be fed pressurized to 0.1-1MPa and preferably 0.3-0.7 MPa by inert gas from the pressurization gassource 78. The depressurization of the interior of the upstream section16 a of the feed conduit and additional optional pressurization of thecleaning fluid causes the cleaning fluid to flow very forcefully intothe interior of the upstream section 16 a of the feed conduit, with theresult that its mechanical scouring action can scrape off materialadhering on the inner wall of the conduit 16 a.

A state is then set up in which the interior of the cleaning targetsection is filled with cleaning fluid (process S15).

After the valve V11 has been opened in process S14 and 1 to 10 secondshave been allowed to elapse, the valve V11 is closed in the instantprocess and a period of quiescence is begun. This sets up a state inwhich the upstream section 16 a of the feed conduit, etc., is filled bythe cleaning fluid fed from the cleaning fluid source 55. This state ismaintained for 1 to 100 seconds for a time suitable for dissolution ofPET-derived residues, for example, 30 seconds.

The interior of the cleaning target section is then pressurized (processS16).

Relative to the situation in the above-described process S15, the valveV2 is opened in the instant process, resulting in the feed of purge gasfrom the purge gas source 57 into the upstream section 16 a of the feedconduit. The interior of the upstream section 16 a of the feed conduitis thereby pressurized by the purge gas to 0.1-1 MPa and preferably0.5-1 MPa. This pressure is preferably higher than the pressure of thecleaning fluid in order to prevent back flow of the cleaning fluid.

The cleaning fluid is then discharged from the cleaning target section(process S17).

Relative to the situation in the above-described process S16, the valveV5 is opened in the instant process, resulting in recovery of the spentcleaning fluid in the upstream section 16 a of the feed conduit throughthe exhaust conduit 25 to the waste tank 62. At this point, the wastetank 62 and exhaust conduit 25 can, as necessary or desired, have beenpreliminarily depressurized by the vacuum exhaust member 63 to 1-30 kPaand preferably to around the vapor pressure of the cleaning fluid atambient temperature. This pressurization of the interior of the upstreamsection 16 a of the feed conduit and additional optional preliminarydepressurization of the waste tank 62 side causes the cleaning fluid toflow very forcefully from the upstream section 16 a of the feed conduit,with the result that its mechanical scouring action can scrape offmaterial adhering on the inner wall of the conduit 16 a.

Processes S13 to S17 are then repeated (process S18).

The above-described processes S13 to S17 are repeated, for example, fora total of 3 to 100 times and preferably 5 to 20 times, until theresidues in the common compartment 38 have been completely cleaned outand removed. Specifically, in the embodiment under consideration thetreatment comprising, inter alia, feed of cleaning fluid and purge gasinto the cleaning target section (upstream section 16 a of the feedconduit) and vacuum exhaust thereof is run repeatedly as a batchtreatment. During this sequence, pressure is applied to the feed anddischarge of the cleaning fluid as described above in order to impart amechanical action to the cleaning fluid. This makes it possible in theembodiment under consideration to conduct an effective cleaning usingsmall amounts of cleaning fluid.

The interior of the cleaning target section is then subjected to a gaspurge (process S19).

Relative to the above-described process S17, the valves V5, V7, and V9are closed in the instant process, thereby elaborating a state in whichthe upstream section 16 a of the feed conduit, etc., is filled by purgegas fed from the purge gas source 57. The valve V2 is then closed andthe valves V5 and V8 are thereafter opened, resulting in discharge ofthe purge gas through the exhaust conduit 25. This procedure is repeateduntil no traces of cleaning fluid remain in the upstream section 16 a ofthe feed conduit.

Then, as necessary the source tank 22 can be detached and switched outfor a fresh source tank. The details of the corresponding operations areomitted here since these operations are substantially the same as thosedescribed above with reference to processes S4 to S8.

EXAMPLES

Cleaning treatment experiments were run using the source liquid supplyapparatus illustrated in FIG. 8. In this experiment, however, thesampling section illustrated in FIG. 9 was used instead of the wastetank 62 structure illustrated in FIG. 8. As illustrated in FIG. 9, anexchangeable sampling section 82 is provided with a sampling bottle 84that is connected to a port conduit 86 that branches from the exhaustconduit 25. A valve VA1 is disposed in the exhaust conduit 25 and avalve VA2 and needle valve VA3 are disposed in the port conduit 86.

The conduit section 16 a comprising the cleaning target section in theseexperiments was made of stainless steel (SS316L) and had an outsidediameter of 6.35 mm, a wall thickness of 1 mm, an electropolishedinterior surface, and a length of 1,000 mm. The source liquid was99.9999% pure PET, the cleaning fluid was ethanol, the purge gas washigh-purity nitrogen, and the source liquid pressurization gas washigh-purity helium.

In the case of example EB (batch treatment), which is an embodiment ofthis invention, apparatus set up and discharge of residual PET in theconduit section 16 a were first carried out according to processes S11and S12 as described above. The interior of the conduit section 16 a wasthen depressurized to 6.5 kPa by the vacuum exhaust member 63 (processS13). This was followed by the supply of ethanol pressurized to 0.3 MPainto the conduit section 16 a (process S14) and then by standing for 5seconds (process S15). The interior of the conduit section 16 a wassubsequently pressurized to 0.6 MPa by N₂ gas (process S16), after whichvalves V5, VA2, and VA3 (see FIGS. 8 and 9) were opened (process S17)and the pressurized ethanol was recovered to the sampling bottle 84 (seeFIG. 9). This cycle of processes S13 to S17 was repeated for a total often times. The Ta concentration in the 20 cm³ of recovered ethanol wasanalyzed in each cycle by inductively coupled plasma-mass spectrometry(ICP-MS).

In the case of comparative example EC (continuous treatment), apparatusset up and discharge of residual PET in the conduit section 16 a werefirst carried out according to processes S11 and S12 as described above.Ethanol pressurized to 0.3 MPa was then fed into the conduit section 16a and by adjusting the valve VA3 a continuous ethanol flow having a flowrate of 20 cm ³/min was produced in the conduit section 16 a. Theethanol discharged from the conduit section 16 a was recovered at theoutlet from the valve VA3 (see FIG. 9) while changing the bottle 84 at1-minute intervals. The Ta concentration in the 20 cm³ of ethanolrecovered in each bottle 84 was analyzed by ICP-MS.

The results of the experiments are reported in the graph in FIG. 11,where the x-axis plots the cumulative ethanol consumption in cm³ and they-axis plots the Ta concentration in ppm. In FIG. 3, the experimentalresults for example EB (batch treatment) are reported with an opencircle while the experimental results for comparative example EC(continuous treatment) are reported with an “x”. As shown in FIG. 3, thedecline in Ta concentration as a function of the cumulative ethanolconsumption was much greater in example EB than in comparative exampleEC. More specifically, it is demonstrated that example EB enables aneffective cleaning to be performed using less cleaning fluid than incomparative example EC.

FIGS. 12 through 16 contain conduit diagrams that in each instanceschematically illustrate a source liquid supply apparatus that isanother embodiment of this invention. The apparatuses in theseembodiments correspond to modifications of the apparatus illustrated inFIG. 8. These apparatuses can be cleaned by carrying out theabove-described processes S11 through S19.

In the apparatus illustrated in FIG. 12, the structural member Com1,which should not be exposed to cleaning fluid, has been preliminarilyinstalled so as to enable it to reside in a bypass from the conduitsection that is the cleaning target. This structural member Com1 can beexemplified by a liquid mass flow controller (MFC), orifice, needlevalve, check valve, pressure controller, and filter. However, thestructural member Com2, for example, a valve or pressure sensor, iscleaned along with the conduit section that is the cleaning target.

In the apparatus illustrated in FIG. 13, the feed conduit 16 is branchedinto conduits 161, 162, and 163, which are themselves directed to threedifferent process facilities. A common cleaning fluid source 55 and acommon purge gas source 57 are connected, using a configuration inconformity with the apparatus illustrated in FIG. 8, to the conduits161, 162, and 163. The conduits 161, 162, and 163 are cleaned, eithersimultaneously or individually, using the above-described processes S11through S19.

In the apparatus (a dual tank structure) illustrated in FIG. 14, twosource tanks 22 and 222 are interchangeably provided via conduits 16 aand 216 for a single process facility 10. The source tank 22, a commoncleaning fluid source 55, and a common purge gas source 57 areconnected, using a configuration in conformity with the apparatusillustrated in FIG. 8, to the additional conduit 216. The conduits 16 aand 216 are alternately cleaned using the above-described processes S11through S19.

In the apparatus illustrated in FIG. 15, an auxiliary source liquid tank322 is connected through the conduit 316 to the source tank 22. Thesource tank 22, a common cleaning fluid source 55, and a common purgegas source 57 are connected, using a configuration in conformity withthe apparatus illustrated in FIG. 8, to the additional conduit 316. Theconduits 16 a and 316 are simultaneously or alternately cleaned usingthe above-described processes S11 through S19.

A second cleaning fluid source 455 and a second waste tank 462 areadditionally disposed in the apparatus illustrated in FIG. 16 in orderto be able to use different cleaning fluids. In this case, a batch modecleaning treatment can be run by the above-described processes S13through S19 using either of the cleaning fluids.

While various modifications and alterations within the technical sphereof the concept of this invention can be devised by the individualskilled in the art, it should be understood that these modifications andalterations also fall within the scope of this invention.

As has been explained in the preceding, this invention provides a sourceliquid supply apparatus that incorporates a cleaning function and thatavoids leaving source liquid- and/or cleaning fluid-derived residues inthe vicinity of the joint or connection region between the source liquidfeed conduit and the source tank. This invention also provides a methodfor detaching the source tank from the foregoing apparatus and a methodfor cleaning the source liquid feed conduit

1. A source liquid supply apparatus comprising: a) a source ofpressurization gas; b) a source of cleaning fluid; c) a source of purgegas; d) a prescribed facility; e) a leaktight source tank comprising adischarge port and a pressurization port, wherein said source tankcontains a source liquid; f) a pressurization gas conduit, wherein saidpressurization gas conduit connects said pressurization port and saidsource of pressurization gas; g) a flow-switching mechanism that isattached to said discharge port, wherein said flow-switching mechanismcomprises; i) a first port, wherein said first port is connected to saiddischarge port, ii) a second port and a third port, which are connectedto each other through an intermediate flow passage and which areconnected to said first port, and iii) a valve member that can producean isolated state in which communication between said first port, saidsecond port, and said third ports is closed off while communicationbetween said second port and said third port is maintained; h) a feedconduit that connects said second port to said prescribed facility; i) acleaning fluid conduit that connects said feed conduit with said sourceof cleaning fluid; j) a purge gas conduit that connects said feedconduit to said source of purge gas; and k) an exhaust conduit thatconnects to said third port.
 2. The source liquid apparatus of claim 1,further comprising an undivided common compartment comprising a firstorifice connected to said first port, a second orifice connected to saidsecond port, a third orifice connected to said third port, and an innerwall.
 3. The source liquid supply apparatus of claim 2, wherein saidundivided common compartment functions as part of said intermediate flowpassage, and said valve member has the ability to close said firstorifice while said second orifice and said third orifice remain open. 4.The source liquid supply apparatus of claim 1, wherein said first portis connected through a first orifice to a partial common compartmentthat functions as part of the intermediate flow passage, said secondport and said third port are connected to each other through aconnection that does not proceed through said partial common compartmentand are connected to said partial common compartment through a commonorifice, and said valve member has the ability to close said commonorifice.
 5. The source liquid supply apparatus of claim 2, wherein saidvalve member is supported by a bellows or a diaphragm that forms a partof said inner wall of said undivided common compartment.
 6. The sourceliquid supply apparatus of claim 1, further comprising a vacuum exhaustmember, wherein said vacuum exhaust member is connected to said exhaustconduit.
 7. The source liquid supply apparatus of claim 1, furthercomprising a first mounting valve and a second mounting valve, whereinsaid first mounting valve is disposed in said feed conduit in thevicinity of said second port, said second mounting valve is disposed insaid exhaust conduit in the vicinity of said third port, and saidflow-switching mechanism is detachable from said first mounting valveand said second mounting valve.
 8. A method for detaching the sourcetank of a source liquid supply apparatus of claim 7, comprising: a)providing a liquid supply apparatus, comprising: i) a source ofpressurization gas; ii) a source of cleaning fluid; iii) a source ofpurge gas; iv) a prescribed facility; v) a leaktight source tankcomprising a discharge port and a pressurization port, wherein saidsource tank contains a source liquid; vi) a pressurization gas conduit,wherein said pressurization gas conduit connects said pressurizationport and said source of pressurization gas; vii) a flow-switchingmechanism that is attached to said discharge port, wherein saidflow-switching mechanism comprises; 1) a first port, wherein said firstport is connected to said discharge port, 2) a second port and a thirdport, which are connected to each other through an intermediate flowpassage and which are connected to said first port, and 3) a valvemember that can produce an isolated state in which communication betweensaid first port, said second port, and said third ports is closed offwhile communication between said second port and said third port ismaintained; viii) a feed conduit that connects said second port to saidprescribed facility; ix) a cleaning fluid conduit that connects saidfeed conduit with said source of cleaning fluid; x) a purge gas conduitthat connects said feed conduit to said source of purge gas; xi) anexhaust conduit that connects to said third port; b) dischargingresidual liquid, wherein said discharging comprises: i) depressurizingsaid exhaust conduit or said source, and ii) discharging source liquidremaining within the feed conduit into said exhaust conduit or saidsource tank by utilizing the pressure difference produced by saiddepressurization; c) feeding cleaning fluid from the cleaning fluidconduit into the feed conduit, wherein said feeding comprises: i)filling the interiors of said feed conduit, said second port, saidintermediate flow passage, and said third port with cleaning fluid, andthen; ii) opening said exhaust conduit and discharging said cleaningfluid into said exhaust conduit, wherein said feeding carried out aftersaid residual liquid discharge process and in which, with said isolatedstate being in place and said exhaust conduit closed; d) purging,wherein said purging comprises: i) feeding purge gas from the purge gasconduit into the feed conduit so as to fill the interiors of said feedconduit, said second port, said intermediate flow passage, and saidthird port with purge gas, and ii) discharging said purge gas into saidexhaust conduit after opening said exhaust conduit; and e) detaching,wherein said detaching comprises detaching said flow-switching mechanismand said source tank from said source liquid supply apparatus bydetaching said flow-switching mechanism from said first mounting valveand said second mounting valve, wherein said detaching is carried outafter said purge process.
 9. The method of claim 8, further comprising;f) interconnecting said feed conduit and said exhaust through said firstmounting valve and said second mounting valve, and flowing purge gasfrom said purge gas conduit through said feed conduit and into saidexhaust conduit.
 10. The method of claim 8, wherein c) and d) arerepeated.
 11. The method of claim 10, wherein step b) comprises: a)closing said exhaust conduit; b) pressurizing said feed conduit to about0.1 to about 1 MPa by feeding said purge gas; and c) opening saidexhaust conduit to discharge said residual liquid into said exhaustconduit.